drm/drv: Remove initialization of static variables

Address the following checkpatch errors:
ERROR: do not initialise statics to false

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/1613701811-32037-1-git-send-email-tiantao6@hisilicon.com